After news emerged of a grisly chemical weapons attack on Syrian civilians, President Donald Trump ordered a cruise missile barrage on the airbase from which the attacks allegedly began. The purpose seemed clear enough. According to the Pentagon, "The strike was a proportional response to Assad's heinous act... The strike was intended to deter the regime from using chemical weapons again."

But while this sounds like a simple story, it has few if any good historical analogies. The United States is now in the odd position of launching air strikes against opposite sides in someone else's civil war.

Perhaps the closest analogies come from U.S. experience dealing with Iraq in the 1990s. During the first Gulf War, the George H.W. Bush administration warned Saddam Hussein against using chemical weapons against U.S. forces or against Israel. The administration desperately wanted to keep Israel from entering the war, which might have shattered the coalition. It issued stern threats and vaguely alluded to a possible U.S. nuclear response. While Iraq fired missiles against Israel, none carried chemical warheads. This experience might have convinced some Trump advisers that something similar might work in Syria. Perhaps nothing can stop Bashar Assad from fighting, but a measured strike might push him to take some of his nastiest weapons out of play.

A U.S. Marine watches a statue of Saddam Hussein being toppled in Firdaus Square in downtown Baghdad on April 9, 2003 file photo. (AP Photo/Jerome Delay, File)

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The Clinton administration also attempted to demonstrate its commitment to preventing Iraq from using unconventional weapons. In 1998 it conducted a four-day bombing campaign to degrade Iraq's supposed arsenal of weapons of mass destruction. President Clinton claimed that the bombing delivered "a powerful message to Saddam. If you act recklessly, you will pay a heavy price."

While these analogies are far from perfect, they do provide a cautionary tale for the current debate about what to do next in Syria. Efforts to deter Iraq in 1991 and 1998 were largely successful. Not only did Hussein eschew chemical weapons during the first Gulf war, but he also shelved his WMD program in the decade that followed. Iraq dismantled its previously large stockpile of weapons and associated materiel. His public bluster in the years after the war, which may have been designed to keep his domestic rivals at bay, betrayed the reality of Iraq's military impotence.

Unfortunately, U.S. officials did not view this as a success story. They worried that Hussein's rhetoric and belligerent attitude toward international weapons inspectors were signs that he had never abandoned his WMD ambitions. Economic sanctions crippled the Iraqi economy and no-fly zones allowed the United States to keep a close eye on Hussein's deteriorating military, but to no avail. Successive presidents agreed that the Iraqi threat was real as long as Hussein remained in charge. Ironically, U.S. concerns rose as Iraqi power withered. Unable to accept that they had effectively dealt with the threat through limited military action, they decided regime change was the only answer.

The key question today is whether President Trump will accept a limited victory. While the Pentagon has portrayed the Tomahawk missile strike narrowly as an effort to deter further chemical weapons use, the administration is flirting with options for regime change. Earlier this month it seemed resigned to Assad's indefinite rule in Syria, but now it is signaling that it will pursue some international effort to oust him.

This remarkable about-face may simply be another sign of Trump's inconsistency, but it may also be part of a historical pattern. The United States finds it hard to restrain itself once the shooting starts. Limited military successes seem hollow, especially against morally odious regimes. In addition, the sheer size of the U.S. military implies that it shouldn't have to settle for anything less than total victory. Why let Saddam Hussein or Bashar Assad remain in power, when the U.S. has the tools to remove them?

The temptation to keep going is powerful, and prominent hawks like Sen. Marco Rubio are already calling for Trump to overthrow the Syrian regime. But this kind of thinking can obscure limited strategic gains, as happened in Iraq. The appeal to moral obligations can also overwhelm strategic judgment and leave the United States overstretched in regions of limited strategic value, at a time in which more serious challenges lurk elsewhere.

Joshua Rovner is a professor of international politics and national security at Southern Methodist University and the director of the Security and Strategy Program. Email: jrovner@smu.edu